Carmona, J. & Darwall, W. (Mediterranean Workshop, Dec. 2004)
Doadrio undertook a 3-month study of all the Jucar river basin and found only 10 individuals of C. arrigonis at one location (Doadrio, I. pers comm). A canal constructed between the Jucar basin and the Trasinase Tajo-Seguna has allowed C. polylepis to enter and out compete C. arrigonis. Based upon this study and previous information it has been observed that that the population has declined by more than 80% in the past 10 years. The area of occupancy (AOO) of the remaining location is estimated at <10 km², qualifying the species for the Critically Endangered category, and the Jucar river basin is considered to be one location due to the nature of the main threat: introduced species.